Apparatus for the recovery of sulphuric acid from industrial waste gases

Abstract

Apparatus and method for the cryothermal recovery of sulfuric acid as predicated on the capture and conversion of sulfur dioxide contained in industrial waste gases. The apparatus includes a waste gas purifier comprising a chamber through which waste combustion gases are passed so as to traverse an ice bed filter means containing ice produced so as to contain entrained oxygen by an independent ice-making machine and chilled by the use of a cryogenic material, preferably liquid nitrogen. The incoming gases may be chilled by recirculating the gases that have passed through the ice filter bed so as to chill the portion of the chamber that is contacted by the incoming gases prior to their passage through the ice filter bed. Oxygen entrainment may be enhanced by the employment of a source of oxygen and the entrained oxygen at the low temperature provided by the ice bed reacts with sulfur dioxide contained in the waste combustion gases by transition through sulfur trioxide to sulfuric acid. The sulfuric acid is contained in melt from the ice filter bed and may be washed out with a spray of cold water.

What is claimed is: 
     
       1. Apparatus for recovering sulfuric acid from industrial waste gases including sulfur dioxide comprising: a vertically extending waste gas purifier of the cryogenic type including a column into the lower end of which the waste gases are admitted, a thermal shock chilling chamber located intermediate the length of the column, ice filter means above said chilling chamber, water spraying means in operative juxtaposition to the thermal shock chilling chamber, washout means located adjacent the bottom of the column, and a gas discharge adjacent the top of the column;   a cylindrical insulated jacket spaced from and surrounding said waste gas purifier so as to define a passageway therebetween;   circulating means connected to the gas discharge portion of the waste gas purifier, and to said passageway in the vicinity of the lower end of the waste gas purifier, the opposite end of said passageway exhausting to the atmosphere;   means for producing ice containing occluded oxygen;   conduit and manifold means connecting said means for producing ice to the ice filter of the waste gas purifier; and   cryogenic means connected to the conduit means for injecting cryogenic material into the ice prior to the admission thereof to the ice filter means of said waste gas purifier whereby, as waste gases are passed through the waste gas purifier, the sulfur dioxide therein is separated from the waste gases and reacts with the water and oxygen evolved from ice crystals within the ice filter means to produce sulfuric acid that is collected at the washout means of the waste gas purifier, with the remaining gases being circulated through the top of said waste gas purifier, through the circulating means, and thence through the passageway preparatory to exhaust to the atmosphere, with said gases passing through the passageway being operative to absorb heat from the waste gases ascending in the waste gas purifier.   
     
     
       2. Apparatus for recovering sulfuric acid as in claim 1 which comprises means for exhausting particulate solid matter contained in the waste gases through the lower end of the column of said waste gas purifier for collection in a container. 
     
     
       3. Apparatus for recovering sulfuric acid as in claim 1 wherein compressed air means are connected to said conduit and manifold means to pressurize the latter while supercooled ice crystals are being conducted to the ice filter means. 
     
     
       4. Apparatus for recovering sulfuric acid as in claim 1 wherein said circulating means includes an insulated duct connected to the gas discharge portion of the waste gas purifier, and an exhaust fan connected to said insulated duct for forcibly withdrawing waste gases from the purifier, and a second duct extended between said exhaust fan and said passageway adjacent the lower end of the waste gas purifier. 
     
     
       5. Apparatus for recovering sulfuric acid as in claim 1 wherein the upper portion of the column of the waste gas purifier adjacent the ice filter means is insulated. 
     
     
       6. Apparatus for recovering sulfuric acid as in claim 1 wherein the cryogenic means comprises a source of liquid nitrogen. 
     
     
       7. Apparatus for recovering sulfuric acid as in claim 1 wherein pressurized oxygen is provided to said conduit and manifold means to pressurize the latter while supercooled ice crystals are being conducted to the ice filter means. 
     
     
       8. Apparatus for recovering sulfuric acid as in claim 1 further including means connected to the ice making means for supplying oxygen to said machine so as to increase the oxygen inclusion within the ice produced by said ice-making machine. 
     
     
       9. Apparatus for recovering sulfuric acid as in claim 8 wherein the ice producing means is further provided with minute quantities of manganese sulphate to increase the solubility of the sulfur dioxide. 
     
     
       10. Apparatus for the manufacture of sulfuric acid which comprises an ice bed chamber, an ice making machine, conveying means for conveying ice crystals produced by said ice making machine so as to be introduced into said ice bed chamber, foraminous support means within said ice bed chamber for supporting ice crystals introduced into said ice bed chamber by said conveying means to form a bed of ice crystals within said ice bed chamber, cryogenic means connected to said conveying means for supercooling said ice crystals so that said ice crystals occur in said supercooled condition in said ice bed, means for directing waste gases containing sulfur oxide through said ice bed in contact with the surfaces of the ice crystals in said bed thereby melting some of the ice crystals with attendant drainage of resulting aqueous melt from residual ice crystals retained on said foraminous support whereby sulfur dioxide contained in said waste gases is absorbed from said gases during their passage through the ice bed, and means below said ice bed for collecting and withdrawing aqueous melt that drains from said ice bed, said ice making machine being separated from said ice bed chamber and being a machine that produces ice crystals by the freezing of water while in out-of-contact relation with said waste gases and with inclusion in said ice crystals of occluded oxygen which is retained in the supercooled ice crystals that are introduced into said ice bed chamber and that form said bed and which is released by the melting of ice crystals contained in said bed during passage of said gases through said bed and reacts upon release with sulfur dioxide absorbed by said bed during travel of said gases through said bed to form sulfuric acid thereby producing sulfuric acid that is contained in the melt that drains from said bed. 
     
     
       11. Apparatus according to claim 10 which comprise oxygen supply means and means for occluding oxygen supplied by said oxygen supply means so as to occur in the ice crystals contained in the ice bed. 
     
     
       12. Apparatus according to claim 10 which comprises cooling means for cooling said gases prior to contact of said gases with ice crystals contained in said ice bed and which also comprises means for removing solid particulate matter from the waste gases prior to contact of said gases with said ice crystals. 
     
     
       13. Apparatus according to claim 12 which further comprises means for mingling water with aqueous melt that drains from said ice bed thereby assisting in the collection and withdrawal of said melt. 
     
     
       14. Apparatus according to claim 12 wherein said cooling means comprises means for spraying water into said waste gases prior to the entry of said waste gases into said ice bed. 
     
     
       15. Apparatus according to claim 12 wherein said cooling means comprises means for directing waste gases cooled by travel through said ice bed and while they are still cold in out-of-contact heat exchange relation with waste gases directed through said ice bed prior to their entry into said ice bed. 
     
     
       16. Apparatus according to claim 10 which also comprises a conditioning chamber disposed underneath said ice bed chamber, means for directing the waste gases upwardly through said conditioning chamber and then through the ice bed in said ice bed chamber, and water spray jet means for directing a spray of water so as to emanate from adjacent the underside of said foramenous support for said ice bed and descend in counter current relation with the upward travel of said gases through said conditioning chamber thereby cooling said gases prior to their entry into the ice bed, directionalizing the flow of the gases through said conditioning chambers so as to be in adjacent relation to the inner surface of said conditioning chamber, and also comingling water comprised in said spray with the melt that drains from said ice bed. 
     
     
       17. Apparatus according to claim 16 which comprises means in adjacent relation to the lower end of said conditioning chamber for separating solid particulate matter from waste gases prior to contact of said gases with spray from said spray jet means. 
     
     
       18. Apparatus according to claim 16 wherein the inner surface of the conditioning chamber is represented by the tubular wall of a passageway disposed about the conditioning chamber, and means for directing gases that have been cooled by travel through said ice bed and that are still cold through said passageway thereby cooling waste gases in contact with the inner surface of the conditioning chamber during travel thereof upwardly through said conditioning chamber prior to entry of said gases into said ice bed. 
     
     
       19. Apparatus according to claim 16 which includes oxygen supply means for introducing oxygen into said ice making machine to increase the amount of oxygen occluded in the ice formed by said ice making machine.